The Analytical Chemistry Core, under the supervision of Dr. Yei-Mei Peng, will continue to provide support and service In the analytical chemistry area to all the proposed projects. The primary responsibility of this Core continues to be the analysis of the submitted biological samples in an accurate and timely manner for the investigators. The specific assays provided by this Core will Include: retinol, retinyl palmitate, beta- carotene, alpha-tocopherol, alpha-tocopheryl acetate, alpha-tocopheryl succinate, difluoromethylornithine (DfMO), nicotinamide, tannic acid, polyamines, prostaglandin E2D BrdU and PCNA labeling index, and mutant Ha-ras gene and p53 gene copy numbers. In addition, the Core will develop methods for the analysis of new compounds and also conduct research on the chemical properties and stability of the compounds of interest to ensure the proper handling and storage of biological samples prior to analysis. To assure the accuracy and consistency of our analytical data, the Core will continue to follow the existing quality control/quality assurance program we developed as well as the program of the National Institute of Standards and Technology. The fatty Acid Analysis Core, under the supervision of Dr. Donald McNamara, will provide service and support In the area of fatty acid analysis for project III. The Cytofluorography Core, under the supervision of Dr. Raymond Taetle, will perform assays to monitor lymphocyte subpopulations in peripheral blood for projects IIC and IVA. This core will also advice project III for the detection of cell surface markers on melanocytes and project IVB for the detection of T- cells that home to the skin.